There is hitherto known a two-color molding process for fabricating a key top having a closed region such as in the number “0” or the letter “B” or “P” (for example, see Patent Document 1, page 3, top right section, line 2, to same page, bottom right section, line 9, and FIGS. 1 and 2).
Connect-through holes are formed respectively on the inside and outside of the closed region on a primary-side molded article being molded by the abovementioned two-color molding process, the connect-through holes running through the primary-side molded article from top to bottom. A slide core is placed on the bottom face side of the primary-side molded article, and the slide core is retracted, whereby resin of the secondary-side molded article is filled inside a lower-side space part formed between the bottom face of the primary-side molded article and the slide core. The filled resin passes through the connect-through hole, and flows into the inside and outside of the closed region formed on the design face side of the primary-side molded article.